1. Field of the Invention
The present invention relates to a pneumatic tire for a heavy duty vehicle, and more particularly to a tire capable of mitigating railway wear which would often occur in the tire of this kind used for continuous travelling at high speed for long distances.
2. Description of the Prior Art
In general, a radial tire including metal cords for the reinforcement of belts has various advantages such as high wear-resistant property, punctureproof and the like, because of the tough belts arranged between the tread rubber and carcass plies, which are different from those of usual bias tires. However, such a radial tire is inferior in comfortability to drive because of the reinforced rigid belts. Apart from use on bad roads, accordingly, radial tires for good roads have been developed and in recent years the demand for the radial tires has been greatly increased as the road situation improves with development and completion of superhighways.
For such applications, the tread of the tire is formed with circumferentially extending zigzag ribs in view of the traction and brake performances and wear-resistant property and for preventing heating in consideration of the circumferentially extending zigzag patterns in the conventional tires. Such a tread pattern is generally referred to as "rib-type" pattern.
Such ribs are usually continuous in the circumferential direction of the tire. It has been found that extraordinary wears (referred to as "irregular" wear hereinafter) which never occurred in tires, occur upon straight continuous travelling for long distances at high speeds.